Chemical Bonding and Molecular Structure Test -10

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Chemical Bonding and Molecular Structure Test -10

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Weekly Quiz Competition

Question 1
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If the electronic configuration of an element is $1s^2\, 2s^2\, 2p^6\, 3s^2\, 3p^6\, 3d^2\, 4s^2$, the four electrons involved in chemical bond formation will be.....

A
$3p^6$

B
$3p^6, 4s^2$

C
$3p^6, 3d^2$

D
$3d^2, 4s^2$

Solution

In bonding, valence electrons and electrons from penultimate shell participate. In transition elements ns electrons and (n - 1)d electrons participate.
Question 2
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Which of the following angle corresponds to $sp^2$ hybridisation?

A
90°

B
120°

C
180°

D
109°

Solution

As a result of $sp^2$ hybridization geometry is triangular planar forming an angle of 120° with each other.

Question 3

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The electronic configurations of three elements, A, B and C are given below. Answer the questions on the basis of these configurations.

A	$1s^2$	$2s^2$	$2p^6$
B	$1s^2$	$2s^2$	$2p^6$	$3s^2$	$3p^3$
C	$1s^2$	$2s^2$	$2p^6$	$3s^2$	$3p^5$

Stable form of A may be represented by the formula :

$A$

$A_2$

$A_3$

$A_4$

Solution

Octate of A is complete.

Question 4

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The electronic configurations of three elements, A, B and C are given below. Answer the questions on the basis of these configurations.

A	$1s^2$	$2s^2$	$2p^6$
B	$1s^2$	$2s^2$	$2p^6$	$3s^2$	$3p^3$
C	$1s^2$	$2s^2$	$2p^6$	$3s^2$	$3p^5$

Stable form of C may be represented by the formula :

$C$

$C_2$

$C_3$

$C_4$

Solution

KK$[\sigma\,2s]^2$$[\sigma^*\,2s]^2$$[\pi\,2p_x]^2$$[\pi\,2p_y]^2$

bond order = $1\over2$ [6 - 2] = 2

Question 5

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The electronic configurations of three elements, A, B and C are given below. Answer the questions on the basis of these configurations.

A	$1s^2$	$2s^2$	$2p^6$
B	$1s^2$	$2s^2$	$2p^6$	$3s^2$	$3p^3$
C	$1s^2$	$2s^2$	$2p^6$	$3s^2$	$3p^5$

The molecular formula of the compound formed from B and C will be

$BC$

$B_2C$

$BC_2$

$BC_3$

Solution

B represents phosphorus (P) and C represents Chlorine (Cl). The compound formed is $PCl_3$ i.e., $BC_3$.

Question 6

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The electronic configurations of three elements, A, B and C are given below. Answer the questions on the basis of these configurations.

A	$1s^2$	$2s^2$	$2p^6$
B	$1s^2$	$2s^2$	$2p^6$	$3s^2$	$3p^3$
C	$1s^2$	$2s^2$	$2p^6$	$3s^2$	$3p^5$

The bond between B and C will be

Ionic

Covalent

Hydrogen

Coordinate

Solution

Both B and C are non-metals so, the bond formed between them will be covalent.

Question 7
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Which of the following statements are correct about $CO_3^{2-}$?

(i) The hybridisation of central atom is $sp ^3 $.

(ii) Its resonance structure has one C-O single bond and two C=O double bonds.

(iii) The average formal charge on each oxygen atom is 0.67 units.

(iv) All C-O bond lengths are equal.

A
(i),(ii)

B
(ii),(iii)

C
(iii),(iv)

D
(i),(iv)

Solution

In resonating structures bonds are not fixed and therefore, all bond lengths are equal.
Question 8
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In the following questions a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question.

Assertion (A): Among the two O-H bonds in $H_2O$ molecule, the energy required to break the first O-H bond and the other O-H bond is the same.

Reason (R): This is because the electronic environment around oxygen is the same even after breakage of one O-H bond.

A
A and R both are correct, and R is correct explanation of A

B
A and R both are correct, but R is not the correct explanation of A

C
A is true but R is false

D
A and R both are false

Solution

Correct assertion: The bond enthalpy in H-O-H is not same for both the O-H bonds.

Correct reason: Because electronic charge on oxygen atom is different after breaking of one O-H bond.

Question 9

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Match the items given in Column I with examples given in Column II.

Column I	Column II
(i) Hydrogen bond	(a) C
(ii) Resonance	(b) LiF
(iii) Ionic solid	(c) $H_2$
(iv) Covalent solid	(d) HF
	(e) $O_3$

(i) → (e) (ii) → (d) (iii) → (b) (iv) → (a)

(i) → (d) (ii) → (e) (iii) → (b) (iv) → (a)

(i) → (d) (ii) → (e) (iii) → (a) (iv) → (b)

(i) → (b) (ii) → (d) (iii) → (a) (iv) → (e)

Question 10
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Dimagnetic species are those which contain no unpaired electrons. Which among the following are dimagnetic?

(i) $N_2$

(ii) $N_2^{2-}$

(iii) $O_2$

(iv) $O_2^{2-}$

A
(i),(ii)

B
(ii),(iii)

C
(iii),(iv)

D
(i),(iv)

Solution

In both the species all orbitals have paired electrons.
Question 11
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Which of the following order of energies of molecular orbitals of $N_2$ is correct?

A
$(\pi2p_y)<(\sigma2p_x)<(\pi^*2p_x)\approx (\pi^*2p_y)$

B
$(\pi2p_y)>(\sigma2p_x)>(\pi^*2p_x)\approx (\pi^*2p_y)$

C
$(\pi2p_y)<(\sigma2p_x)>(\pi^*2p_x)\approx (\pi^*2p_y)$

D
$(\pi2p_y)>(\sigma2p_x)<(\pi^*2p_x)\approx (\pi^*2p_y)$

Solution

Molecules like $B_2 $, $C_2$ & $N_2$ having 1 to 3 electrons in p orbital energy of $\sigma2p$ molecular orbital is greater than that of $\pi2p_x$ and $\pi2p_y$ molecular orbitals.
Question 12
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Species having same bond order are:

(i) $N_2$

(ii) $N_2^-$

(iii) $F_2^+$

(iv) $O_2^-$

A
(iii),(iv)

B
(i),(iv)

C
(ii),(iii)

D
(i),(ii)

Solution

In both the species number of electrons in bonding molecular orbital and in antibonding orbital are same.
Question 13
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Which of the following statements are not correct?

(i) NaCl being an ionic compound is a good conductor of electricity in the solid state.

(ii) In canonical structures, there is a difference in the arrangement of atoms.

(iii) Hybrid orbitals form stronger bonds than pure orbitals.

(iv) VSEPR Theory can explain the square planar geometry of $X_eF_4 $.

A
(i),(iv)

B
(i),(ii)

C
(iii),(ii)

D
(iii),(iv)

Solution

In first statement ions are not free in solid state but they are strongly bonded through electrostatic forces and second statement it does not show canonical structures being ionic compounds.
Question 14
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Match the shape of molecules in Column I with the type of hybridisation in Column II.

Column I Column II

(i) Tetrahedra (a) $sp^2$

(ii) Trigonal (b) sp

(iii) Linear (c) $sp^3$

A
(i) → (b) (ii) → (a) (iii) → (c)

B
(i) → (c) (ii) → (b) (iii) → (a)

C
(i) → (c) (ii) → (a) (iii) → (b)

D
(i) → (a) (ii) → (c) (iii) → (b)
Question 15
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Which of the following statement is not correct from the view point of molecular orbital theory?

A
$Be_2$ is not a stable molecule

B
$He_2$ is not stable but $He ^+$ is expected to exist

C
Bond strength of $N_2$ is maximum amongst the homonuclear diatomic molecules belonging to the second period

D
The order of energies of molecular orbitals in $N_2$ molecule is $\sigma$2s < $\sigma^*$2s < $\sigma$2$p_z$ < ($\pi$2$p_x$ = $\pi$2$p_y$) < $\sigma^*2p_z$

Solution

The energy of a $\sigma2p$ molecular orbital is greater than that of $\pi2p_x$ and $\pi2p_y$ molecular orbitals.
Question 16
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Which of the following options represents the correct bond order?

A
$O_2^->O_2>O_2^+$

B
$O_2^-<O_2<O_2^+$

C
$O_2^->O_2<O_2^+$

D
$O_2^-<O_2>O_2^+$

Solution

$N_b$ electrons > $N_a$ electrons and also depends on bond order.

B.O = $1\over2$($N_b$ - $N_a$)
Question 17
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The electronic configuration of the outermost shell of the most electronegative element is

A
$2s^22p^5$

B
$3s^23p^5$

C
$4s^24p^5$

D
$5s^25p^2$

Solution

Elements of Group 17 has $ns^ 2np ^5$ electronic configuration. The electronegativity decreases down the group. The elements of this group are most electronegative.
Question 18
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Amongst the following elements whose electronic configurations are given below, the one having the highest ionisation enthalpy is

A
$[Ne]3s^23p^1$

B
$[Ne]3s^23p^3$

C
$[Ne]3s^23p^2$

D
$[Ar]3d^{10}4s^24p^3$

Solution

Since half-filled p-orbital is more stable as compared to partially filled orbital.
Question 19
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According to molecular orbital theory, which of the following is true with respect to $Li_2^+$ and $Li_2^-$ ?

A
Both are stable

B
Both are unstable

C
$Li_2^+$ is unstable and $Li_2^-$ is stable

D
$Li_2^+$ is stable and $Li_2^-$ is unstable

Solution

Both $Li_2^+$ and $Li_2^-$ has 0.5 bond order and hence both are stable.
Question 20
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For the chemical reaction $N_{2(g)}+3H_{2(g)} \rightleftharpoons 2NH_{3(g)}$ The correct option is

A
$-{d[N_2] \over dt}=2{d[NH_3]\over dt}$

B
$-{d[N_2] \over dt}=\frac{1}{2}{d[NH_3]\over dt}$

C
$3{d[N_2] \over dt}=2{d[NH_3]\over dt}$

D
$-\frac{1}{3}{d[N_2] \over dt}=-\frac{1}{2}{d[NH_3]\over dt}$

Solution

$N_{2}+3H_{2} \rightleftharpoons 2NH_{3}$

Rate of reaction is given as

$-{d[N_2] \over dt}=-\frac{1}{3}{d[H_2]\over dt}= +\frac{1}{2} {d[NH_3]\over dt}$
Question 21
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Which of the following phenomena will occur when two atoms of the elements having same spin of electron approach for bonding?

A
Orbital overlap will not occur

B
Bonding will not occur

C
Both $$A$$ and $$B$$ are correct

D
None of the above

Solution

When two atoms of the elements having the same spin of electron approach for bonding, the orbital overlap will not occur and bonding will not occur. Hence, Both $$(A)$$ and $$(B)$$ are correct.
However, if two atoms of the elements having opposite spin of electron approach for bonding, the orbital overlap will occur and bonding will not occur.
Question 22
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In $${ PO }_{ 4 }^{ 3- }$$, the formal charge on each oxygen atom and the $$P-O$$ bond order respectively are:

A
$$-0.75,0.6$$

B
$$-0.75,1.0$$

C
$$-0.75,1.25$$

D
$$-3,1.25$$

Solution

In $${ PO }_{ 4 }^{ 3- }$$, the formal charge on each oxygen atom and the $$P-O$$ bond order are $$-0.75,1.25$$ respectively.

$$\left[O-\underset{O}{\underset{||}{\overset{O}{\overset{|}{P}}}}-O\right]^{3-} \leftrightarrow \left[O-\underset{P}{\underset{|}{\overset{O}{\overset{|}{P}}}}=O\right]^{3-}$$

$$\left[O-\underset{O}{\underset{|}{\overset{O}{\overset{||}{P}}}}-O\right]^{3-} \leftrightarrow \left[O=\underset{P}{\underset{|}{\overset{O}{\overset{|}{P}}}}-O\right]^{3-}$$

Bond order $$=\cfrac { \text { Number of bonds} }{ \text {Number of Resonating structures} } =\cfrac { 5 }{ 4 } =1.25$$

In a given resonance structure, the O atom that forms double bond has formal charge of 0 and the remaining 3 O atoms have formal charge of -1 each.
In the resonance hybrid, a total of -3 charge is distributed over 4 O atoms. Thus the formal charge of each O atom is $$\dfrac {-3}{4} = -0.75$$.

Note:
To calculate the formal charge, the following formula is used.
Formal Charge $$=$$ [Number of valence electrons on atom] $$–$$ [non-bonded electrons $$+$$ number of bonds]

For O atom that forms double bond with P atom,
Formal Charge $$=$$ 6] $$–$$ [4 $$+$$2] $$=$$ 0.

For O atom that forms single bond with P atom,
Formal Charge $$=$$ 6] $$–$$ [6 $$+$$1] $$=-$$ 1.
Question 23
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The electro valency theory explains that atoms are held together by an___________that resulted due to transfer or sharing of electrons.

A
repulsive forces

B
attractive forces

C
binding forces

D
none of these

Solution

The two main ways in which atoms can be combined to form molecules are by electrovalent bonds and covalent bonds.Electrovalent bonds are held together by an electrical attraction between positively charged cations and negatively charged anions.
The Valence Bond theory describes the formation of covalent bonds from the overlap of atomic orbitals on two different atoms. Because of the overlap, it is highly probable that a pair of electrons are found in the physical region or space where the orbitals overlap.
Question 24
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Molecule which contains only sigma bonds in it is:

A
Pentene

B
Pentane

C
Pentadiene

D
Pentyne

Solution

The molecules $$A, C & D$$ are alkene, alkyne and alkadiene. They contain both $$\sigma$$ and $$\pi$$ bonds. Alkanes undergo $$sp^3$$ hybrid orbitals and do not contain any $$\pi$$ bonds. They contain only $$\sigma$$ bonds.
Question 25
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A triple bond may be best described as :

A
two sigma bonds and one $$\pi$$ bond

B
one sigma bond and two $$\pi$$ bonds

C
two sigma bonds and two $$\pi$$ bonds

D
three $$\sigma$$ bonds

E
three $$\pi$$ bonds

Solution

A triple bond can be considered as one sigma bond and two pi bonds. The head-on overlap between two $$p_{x}$$ orbitals of two-atom forms the sigma bond. The lateral/ or sideway overlap between $$p_{y}$$ and $$p_{z}$$ orbitals forms two $$\pi $$ bonds. So the correct option is B
Question 26
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Which of the following species has incomplete octet?

A
$$SiF_4$$

B
$${ N }^{ 3- }$$

C
$$Pbr5$$

D
$${B}^{3-}$$

Solution

$$B^{3-} - 1s^22s^22p^4$$
incomplete octet
Question 27
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The $$O-H$$ bond length in $$H_2O$$ is $$xA^0$$. The $$O-H$$ bond length in $$H_2O_2$$ is:

A
$$< \ x \ A^0$$

B
$$x \ A^0$$

C
$$> \ x \ A^0$$

D
$$2x \ A^0$$

Solution

In solid phase $$O-H$$ bond length in $$H_2O_2$$ is 98.8 pm and in gaseous phase it is 95 pm. But $$O-H$$ bond length in water is always 96pm.
Question 28
1 / -0

The number of lone pairs available on the central atom of sulphur tetrafluoride is :

A
$$0$$

B
$$1$$

C
$$2$$

D
$$3$$

Solution

$$ \mathrm SF_{4}: sp^{3}d $$
$$1$$ Lone pair of electrons.
Question 29
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A chemical bond between two atoms is:

A
The tunnel in an atom through which the other one can pass

B
The energy of the individual atoms

C
The link between them

D
A third, connecting atom

Solution

Solution:- (C) The link between atom
Explanation:-
A chemical bond in is a chemical link between two atoms or ions in which the electron pairs are shared between them.
Question 30
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How many unpaired electrons are present in $$N_2^+$$ :

A
1

B
2

C
3

D
4

Solution

According to MOT, $$N_2^+$$ ion has one unpaired electron.

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A	\(1s^2\)	\(2s^2\)	\(2p^6\)
B	\(1s^2\)	\(2s^2\)	\(2p^6\)	\(3s^2\)	\(3p^3\)
C	\(1s^2\)	\(2s^2\)	\(2p^6\)	\(3s^2\)	\(3p^5\)

A	\(1s^2\)	\(2s^2\)	\(2p^6\)
B	\(1s^2\)	\(2s^2\)	\(2p^6\)	\(3s^2\)	\(3p^3\)
C	\(1s^2\)	\(2s^2\)	\(2p^6\)	\(3s^2\)	\(3p^5\)

A	\(1s^2\)	\(2s^2\)	\(2p^6\)
B	\(1s^2\)	\(2s^2\)	\(2p^6\)	\(3s^2\)	\(3p^3\)
C	\(1s^2\)	\(2s^2\)	\(2p^6\)	\(3s^2\)	\(3p^5\)

A	\(1s^2\)	\(2s^2\)	\(2p^6\)
B	\(1s^2\)	\(2s^2\)	\(2p^6\)	\(3s^2\)	\(3p^3\)
C	\(1s^2\)	\(2s^2\)	\(2p^6\)	\(3s^2\)	\(3p^5\)

Column I	Column II
(i) Tetrahedra	(a) \(sp^2\)
(ii) Trigonal	(b) sp
(iii) Linear	(c) \(sp^3\)

Chemical Bonding and Molecular Structure Test -10

Result

Chemical Bonding and Molecular Structure Test -10

Score

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Rank

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SHARING IS CARING

Question 1

\(3p^6\)

\(3p^6, 4s^2\)

\(3p^6, 3d^2\)

\(3d^2, 4s^2\)

Solution

Question 2

90°

120°

180°

109°

Solution

Question 3

\(A\)

\(A_2\)

\(A_3\)

\(A_4\)

Solution

Question 4

\(C\)

\(C_2\)

\(C_3\)

\(C_4\)

Solution

Question 5

\(BC\)

\(B_2C\)

\(BC_2\)

\(BC_3\)

Solution

Question 6

Ionic

Covalent

Hydrogen

Coordinate

Solution

Question 7

(i),(ii)

(ii),(iii)

(iii),(iv)

(i),(iv)

Solution

Question 8

A and R both are correct, and R is correct explanation of A

A and R both are correct, but R is not the correct explanation of A

A is true but R is false

A and R both are false

Solution

Question 9

(i) → (e) (ii) → (d) (iii) → (b) (iv) → (a)

(i) → (d) (ii) → (e) (iii) → (b) (iv) → (a)

(i) → (d) (ii) → (e) (iii) → (a) (iv) → (b)

(i) → (b) (ii) → (d) (iii) → (a) (iv) → (e)

Question 10

(i),(ii)

(ii),(iii)

(iii),(iv)

(i),(iv)

Solution

Question 11

\((\pi2p_y)<(\sigma2p_x)<(\pi^*2p_x)\approx (\pi^*2p_y)\)

\((\pi2p_y)>(\sigma2p_x)>(\pi^*2p_x)\approx (\pi^*2p_y)\)

\((\pi2p_y)<(\sigma2p_x)>(\pi^*2p_x)\approx (\pi^*2p_y)\)

\((\pi2p_y)>(\sigma2p_x)<(\pi^*2p_x)\approx (\pi^*2p_y)\)

Solution

Question 12

(iii),(iv)

(i),(iv)

(ii),(iii)

(i),(ii)

Solution

Question 13

\((\pi2p_y)<(\sigma2p_x)<(\pi^2p_x)\approx (\pi^2p_y)\)

\((\pi2p_y)>(\sigma2p_x)>(\pi^2p_x)\approx (\pi^2p_y)\)

\((\pi2p_y)<(\sigma2p_x)>(\pi^2p_x)\approx (\pi^2p_y)\)

\((\pi2p_y)>(\sigma2p_x)<(\pi^2p_x)\approx (\pi^2p_y)\)

The order of energies of molecular orbitals in \(N_2\) molecule is \(\sigma\)2s < \(\sigma^\)2s < \(\sigma\)2\(p_z\) < (\(\pi\)2\(p_x\) = \(\pi\)2\(p_y\)) < \(\sigma^2p_z\)